Carbon-based Metal Phthalocyanine Axial Complex And Its Supported Fibers For Catalytic Degradation Of Organic Pollutants

With the rapid development of industrialization and urbanization,the threat of environmental and energy crisis is increasingly intensified,especially the new organic pollutants in the environment and ecosystem.These organic pollutants have the characteristics of complex structure and difficult to degrade.When these organic pollutants contaminate water bodies,they have more serious effects on the growth and development of organisms,and ultimately cause immeasurable harm to human health.Therefore,the efficient treatment of new organic pollutants in water has become a major problem restricting the sustainable development of national economy.For toxic and harmful pollutants,the main treatment methods include adsorption,coagulation-flocculation,biological method and advanced oxidation processes.Adsorption and coagulation-flocculation only transfer the organic pollutants to a different phase,and can not completely remove the organic pollutants.The concentration of organic pollutants in membrane filtration is high,which can easily cause secondary pollution to the environment.The biological treatment of organic pollutants covers a large area and has a long treatment cycle,and the organic pollutants are toxic to microorganisms,leading to the reduction of their decomposition efficiency.Advanced oxidation processes catalyze activated oxidants to produce hydroxyl free radicals and other active species,but these free radicals move rapidly in the water,resulting in poor selectivity with organic pollutants in the water,and easy oxidation of the catalyst itself leads to deactivation,thus affecting the recycling performance of the catalyst.In order to improve the selectivity of the catalyst to substrate and its own stability,inspired by the structure and catalytic mechanism of biological enzymes,this paper designed and prepared carbon-based phthalocyanine axial complex catalyst to build a catalyst system for producing high-valent iron-oxo species for catalytic degradation of organic pollutants in water.In order to facilitate the separation and recycling of the catalyst,the catalyst was supported on the fiber to study its catalytic performance and mechanism of catalytic oxidation degradation of organic pollutants in water.In this paper,the stable structure of iron hexadecachlorophthalocyanine(FePcCl₁₆)was synthesized.The multiwalled carbon nanotubes（MWCNTs）were grafted with pyridine（Py）group.The catalyst FePcCl₁₆-Py-MWCNTs was prepared by axial coordination N atoms in Py with iron ions in the center of FePcCl_16.In the experiment,p-chloro-m-xylenol（PCMX）was selected as the model pollutant and hydrogen peroxide（H₂O₂）was used as the oxidant to catalyze degradation of PCMX under simulated solar light irradiation.The results show that the catalytic system has excellent catalytic performance under acidic and neutral conditions,and its catalytic performance is better than that of FePcCl₁₆ adsorbed on MWCNTs(FePcCl₁₆-MWCNTs).The capture experiments of isopropyl alcohol（IPA）,p-benzoquinone（P-BQ）and electron paramagnetic resonance（EPR）,gas chromatography-mass spectrometry（GC-MS）,high resolution mass spectrometry（HDMS）were used to prove that the main active species for the catalytic oxidation degradation of PCMX by the catalytic system were high-valent iron-oxo species.Electrochemical experiments showed that simulated solar light irradiation can enhance the electron transfer between FePcCl₁₆ and MWCNTs to promote the production of high-valent iron-oxo species and enhance the catalytic performance of the system.In order to enhance the catalytic performance of the catalytic system,the axial coordination catalyst FePcCl₁₆-Py-CB was prepared by porous carbon black（CB）.The catalytic performance of FePcCl₁₆-Py-CB was better than that of FePcCl₁₆-Py-MWCNTs due to the strong adsorption capacity of FePcCl₁₆-Py-CB for substrate,and the simulated solar light irradiation had almost no effect on the catalytic performance of FePcCl₁₆-Py-CB.In order to further study the catalytic performance of FePcCl₁₆-Py-CB,dexamethasone（DXMS）,a more complex structure of the hormone model pollutant,was selected to conduct catalytic oxidation experiments at room temperature.The results showed that the catalytic system exhibited excellent catalytic performance under both acidic and neutral conditions.The catalytic performance of the system did not decrease significantly after 6 cycles of use,IPA,P-BQ capture experiments and EPR,GC-MS proved that the main oxidizing activity species in the catalytic system were high-valent iron-oxo species,followed by hydroxyl radicals and superoxide radicals.In order to make the catalyst easy to be recycled after separation from water,the low melting point sheath-core composite polyester fibers（LMPET）were thermally bonded to FePcCl₁₆-Py-CB,and LMPET supported catalyst FePcCl₁₆-Py-CB/LMPET was obtained.FePcCl₁₆-Py-CB/LMPET was characterized by scanning electron microscopy（SEM）,energy dispersive spectroscopy（EDS）,X-ray diffraction（XRD）,differential scanning calorimetry（DSC）and X-ray photoelectron spectroscopy（XPS）proved that FePcCl₁₆-Py-CB had been thermally embedded on the surface of LMPET.FePcCl₁₆-Py-CB/LMPET was used as catalyst to catalyze the activation of H₂O₂ to degrade DXMS at room temperature.The results showed that the catalytic system had excellent catalytic performance under acidic and neutral conditions.After five cycles,the catalytic oxidation degradation rate of DXMS was still above 92%.IPA,P-BQ capture experiments and EPR,GC-MS proved that the catalytic mechanism was still dominated by hight-valent iron-oxo species in the catalytic system.In order to improve the catalytic performance of fiber-supported catalyst,poly（lactic acid）porous nano-fiber supported FePcCl₁₆-Py-CB,namely FePcCl₁₆-Py-CB/PLAPNFs were prepared by centrifugal-electrostatic spinning in the mixed solution of dichloromethane/dimethylacetamide（DCM/DMAC）by blending FePcCl₁₆-Py-CB and PLA.SEM,XRD and XPS showed that FePcCl₁₆-Py-CB was uniformly dispersed on PLAPNFs.FePcCl₁₆-Py-CB/PLAPNFs were used as catalyst for the catalytic activation of H₂O₂ to degrade DXMS.The results showed that the catalytic system had excellent catalytic performance under acidic and neutral conditions,while the catalytic performance was slightly reduced under alkaline conditions.It is noteworthy that the calculated catalytic performance of FePcCl₁₆-Py-CB/PLAPNFs was 6.5 times that of FePcCl₁₆-Py-CB/LMPET.The degradation rate of DXMS was still above 90%after 5cycles.IPA,P-BQ capture experiments and EPR,GC-MS proved that the catalytic mechanism did not change in the catalytic system.